1. Field of the Invention
The invention relates to an apparatus for the filtration of liquids. The invention also relates to a filter cartridge for an apparatus of this type.
2. Description of the Related Art
Filter cartridges are to be understood as meaning on the one hand cartridges which have a screen-like formation for mechanical filtration. On the other hand, filter cartridges are also to be understood as meaning cartridges which, in addition to a screen-like formation, contain at least one filter medium, e.g. in granule form, which is used for the chemical and/or mechanical removal of organic and/or inorganic contaminants and/or to lower the levels of such contaminants. Filter cartridges equipped in this way therefore allow non-mechanical filtration, which may be combined with mechanical filtration. These filter cartridges are used to optimize water, the term optimization being understood as meaning mechanical and/or non-mechanical filtration. This includes, for example, softening and decalcification of drinking water.
A very wide range of embodiments of apparatuses for the filtration of liquids are known.
By way of example, there are filter apparatuses with spherical filter cartridges, which are screwed onto the inlet funnel from below by means of a bayonet catch, as described in WO 2004/014519 A2.
DE 199 05 601 A1 has disclosed an apparatus for the treatment of liquids, having an inlet funnel which has a receiving opening with a sealing rim. The filter cartridge is likewise fitted into the receiving opening from below and is pressed into the receiving opening by means of a separate securing ring. For this purpose, the filter cartridge is provided with a groove on the cartridge upper part below the sealing rim; the lower portion of the securing ring engages in this groove. The upper portion of the securing ring is guided in a groove of a connection piece formed integrally on the funnel base. The filter cartridge is complex to install and remove, requiring particular skill on the part of the operator.
Other embodiments provide for the inlet funnel to have, in its base wall, a receiving opening, into which the filter cartridge is fitted from above. The filter cartridge generally has a conical sealing rim, which bears against the edge of the receiving opening. The filter cartridge may become tilted during insertion, so that the intended sealing position is not adopted.
DE 199 158 29 A1 has disclosed a filter cartridge and an apparatus for treating liquids, in which the sealing rim has additional latching means, which interact with corresponding latching means in the region of the opening in the base of the inlet funnel. The latching means are brought into engagement with one another by a rotational movement.
In this embodiment, the filter cartridge is held only at the edge and is located in the filtrate space. If the apparatus is a kettle, therefore, the filter cartridge is also in the boiling space, which means that the filter cartridge could be damaged during the heating of the filtered liquid. Therefore, it is desirable for the filter cartridge to be arranged such that it is shielded from the filtrate space or boiling space.
Inlet funnels with a receiving chamber for the filter cartridge are used to remedy this problem. In this design too, the conical sealing rim of the filter cartridge bears against the rim of the receiving opening in the base wall of the inlet funnel.
The peripheral and base wall of the filter cartridge is arranged at a distance from the peripheral and base wall of the receiving chamber, so that during filtration, although filtered liquid can collect in this intermediate space, this liquid does not limit the quantitative flow through the apparatus. An outflow opening provided with a closure element is located in the base wall of the receiving chamber.
DE 198 46 583 A1 has disclosed a water filter device of this type, with a collection can and a heating element. The inlet funnel has a receiving chamber, into which the filter cartridge is fitted from above. The receiving chamber is formed by a filter insert, which may be fixedly connected to the inlet funnel or can be fitted into the receiving opening. The filter insert is matched to the conical shape of the filter cartridge and forms a guide element for the filter cartridge. Since the peripheral wall of the filter cartridge bears against the filter insert over its full surface, the two components can only be separated from one another with difficulty, in particular if the user pushes the filter cartridge too deep into the filter insert. On account of the fact that two conical surfaces are sliding along one another, it is not clear to the user when he has reached the limit position which is required for optimum seating of the filter cartridge and defines the sealing position of the filter cartridge.
U.S. Pat. No. 4,020,350 describes a filter system which is connected to a water pipe via two connections. The filter system comprises a housing upper part and a housing lower part, which are screwed together after the filter cartridge has been fitted. The cover and base wall of the filter cartridge have cup-shaped indentations, in which correspondingly shaped connection pieces of the housing parts for supplying the unfiltered liquid and removing the filtered liquid, engage. To change the filter cartridge, the two housing parts have to be unscrewed.
In all the known filter apparatuses, it is necessary for the filter cartridge to be matched to the desired quantitative flow.